change camera into multi-view camera?
A camera being ‘multi view’ or not isn't a specific camera setting but relates to the configuration of multiple cameras, with one camera object for each 'view'.

If you look at the bottom of the Views panel of your first screenshot you'll see the 'Camera Suffix' property. This can be defined for each 'view' of the camera.

To link the cameras into a 'multi view camera' you simply need to name them to have the camera 'name' (eg, 'Camera') followed by the suffix.

So, for a multi-view camera named 'MyCamera' with views of 'Left' (suffix '_L') and 'Right (suffix '_R') you would name your two cameras 'MyCamera_L' and 'MyCamera_R'. Selecting either camera as the 'active' one will effectively select both for rendering.

All of the defined Views must exist as cameras in the scene for it to be considered "multi-view".

See Is there a way to batch render images from several cameras? and continuous sequence of frames with multiple cameras with each camera starting at start of animation?